Nonvibratory mounting for reproducer arms



Sept. 6, 1932. c T 1,875,848

NONVIBRATORY MOUNTING FOR REPRODUCER ARMS Filed May 19, 1930 INVENTORPatented Sept. 6, 1932 noun 0. near, or rasanana g catmoama HONVIBBATOBYMOUNTING FOB REPRODUOER ARMS Application fled Kay 10, mo. Serial in.453,575.

This invention relates fgenerally to sound reproducing apparatus thetype utilizing mechanical disk records, and is more particularlyconcerned with a vibration absorbing mounting for the swinging arm whichcarries the reproducer pick-up unit in such apparatus.

Sound reproducing apparatus is designed with a particular view towardreducing mechanical vibrations to an absolute minimum, as suchvibrations when transmitted to the ick-u unit introduce seriousdistortions and irregu arities in sound reproduction. It has been foundto be an extremely diflicult prob- 15 lem, however, to so balance andcushion the apparatus that all such vibrations are effectivelyeliminated.

It is the prima object of the present invention to provi e a vibration.absorbing mounting for the arm which carries the reproducer pick-upunit, so that thepick-up unit will be eflectively insulated from all ofthe vibrations in the other parts of the apparatus.

25 According to the present invention, the reproducer arm is provided atits rear end with a resilient, vibration-absorbing mounting on the frameof the ap aratus, which effectively insulates the reproducer arm fromall of the 30 usual vibrations encountered in the normal operation ofthe apparatus. The invention itself will best be understood from thefollowing detailed description of a present preferred embodimentthereof, ref- 35 erence' for this purpose being had to the accompanyingdrawing, in which:

Fig. 1 is, a perspective view of a ty ical record table showing theapplication 0 my improved reproducer arm mounting;

Fig. 2 is a vertical section taken on line 22 of Fig. 1;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 2;

Fig. 4 is a section taken on line 44 of 45 Fig. 2; and

Fig. 5 is a horizontal section taken on line 55 of Fig. 2, parts beingbroken away to show in section.

Referring now to the drawing, the numeral 50 indicates a record table,driven in any usual manner, and upon which is supported and centered aphonograph record 11. 'Extendlng from a frame part 12, from which therecord table 10 is supported, is a bracket 14 which carries at its outerend the reproducer unit generally indicated by the numeral Reproducerunit 15 embodies inthe present instance a tubular arm 16 carrying at itsfree forward end a pick-up unit of usual constructlon, a'nd pivotallyand resiliently mounted at its rear end, as now to be described, uponthe outer end of bracket 14.

The outer end of bracket 14 supports a base member 20 for the reproducermounting, which member is positioned on bracket 14 by means of a pin 21fitted thereinto, and which carries a vertical tube 22 into which isfitted a rubber cushion 23 for the mounting of the reproducer arm.Cushion 23 carries a coaxial bearing sleeve 25 for the pivot pin 26 ofthe reproducer arm supporting frame 28, frame 28 being verticallysupported by means of its shoulder 29 which rests on the upper end ofsleeve 25.

Frame 28 has in the present embodiment, two oppositely extending arms 30carrying at their outer ends rings 31, which rings are disposed withtheir axis horizontal and parallel. A coil spring 33 is secured at itsouter end within each of the rings 31.

The rear end of tube 16 carries a yoke 36 embodying a pair of oppositelyextending arms 37, which arms are secured at their outer ends to theinner ends of coil springs 33. For this purpose the inner ends ofsprings 33 may be soldered or otherwise secured to the shank of a headedscrew 40 carried by the ends of yoke arms 37, as clearly shown in Figs.4 and 5. The inner portion of each spring is confinedbetween washers 41and 42 on screw 40, while a soft rubber disk or cushion 43 is providedoutside of washer 41, the whole assembly being held together by a nut 44on the end of screw 40.

The leads from the pick-up unit preferably pass through the tubular arm16, as shown, so that they will not drag over the surface of the record.

The reproducer arm is free to pivot at its rear end to allow its pick-upunit to follow the record groove by rotation of pin 26 in bearingsleeve; and the coil springs 33 allow the arm to be raised to lift thepick-up unit off the record. When the reproducer arm is not in use it issupported by a rest 56 carried by the base member 20 of the mounting.

The rubber cushion 23 in which the supporting pin 26 of the mounting iscarried aids in insulating the reproducer unit from the vibrations ofthe supporting bracket 14. The chief vibration-absorbing element,however, is the resilient spring-support of the reproducer arm, which isof sufficientflexibility to absorb every perceptible vibration of thesupporting bracket arising in normal operation and, except for anyunusual movements of the apparatus, supports the reproducer arm andpick-up unit in substantially perfect steadiness.

Thus, since the reproducer arm is carried by the centers of the coilsprings, the usual vibrations in the apparatus may cause the outer endsof the springs to be correspondingly vibrated in an axial direction,that is, longitudinally of the reproducer arm, andalso to becorrespondingly vibrated laterally in any direction, without suchvibrations being transmitted through the springs with suf ficient energyto overcome the inertia of the reproducer arm and the pickup unitsufficiently to set up the slightest perceptible vibrations thereof.

The drag of the record on the pick-up unit tends to stretcher extend thecoil springs forwardly, as illustrated in Fig. 5,and especi ally is thiseffect noticeable at the lower frequencies. To. curtail this effect therubber cushions or disks 43 are provided, which resiliently contact theback edges of rings 31 and thereby prevent more than an allowableextensionof the springs. The resiliency of the rubber disks, however,similarly to that of the coil springs, cause them likewise to absorbvibrations of the reproducer mounting and to prevent their transmissionto the pick-up unit.

- It will be understood the drawing and description are to be consideredmerely as illustrative of and. not restrictive on the broader claimsappended hereto, for various changes in design, structure andarrangement may be made without departing from the spirit and scope ofsaid claims.

I claim 1. In sound reproducing apparatus, the combination of a frameadapted for support of a rotatable record table,'a reproducer arm, amounting for said reproducer arm on said frame, and a vibrationabsorbing unit included in the mount ng of said reproducer arm; saidmounting including a member pivoted to said frame, a pair of coilsprings each supported at one end of its coil by said memher, said coilsbeing relatively disposed with idly connected at one of its ends totheir axes parallel and in spaced relation, a.

reproducer arm extending parallel to said coil axes, and a supportingconnection between the opposite end of each of said coil springs andsaid reproducer arm, said connection ineluding a cushion adaptedresiliently to limit extension of said spring.

2. In sound reproducing apparatus having a frame adapted to support arecord table, areproducer arm, and a coiled spring connected at spacedpoints in its length with the frame and reproducer arm and forming thesole support of the arm on the frame, said spring eing resilientlyyielding in all directions.

3. In sound reproducing apparatus having a frame adapted to support arecord table a reproducer arm, and a resilient yielding member connectedbetween the reproducer arm and the frame and forming the sole support ofthe arm on the frame, said yielding for rotation on a vertical axis, thecombina tion of a supporting member pivoted with respect to said frameon an axis parallel'to the table axis, a 0011 spring connected at oneend to said supporting member, and arranged with its axis in a planesubstantially at right angles to said table axis, and a reproducer armconnected for its support to the other end of said coil spring andextending substantially in the direction of said coil axis.

5. In sound reproducing apparatus having a frame adapted to support arecord table for rotation on a vertical axis, the combination ofasupporting member pivoted with respect to said frame on an axisparallel to the table axis, a pair of coil springs each rigsaidsupporting member, said coil springs arranged with their axes paralleland extending in planes substantially at right angles to the tale axis,and a reproducer arm connected for its support at its rear end to thefree ends of said coil springs and extending substantially parallel tothe axes of said springs.

6. In sound reproducing apparatus having a frame adapted to support arecord table for rotation on a vertical axis, the combination of asupporting member pivoted with respect to said frame on an axis parallelto the table axis, a spirally coiled spring connected at its outer endto said supporting member and arranged with its axis in a planesubstantially at right angles to the table axis, and a reproducerconnected for its support to the free inner end of said coil spring.

In witness that I claim the foregoing I have hereunto subscribed my namethis 24 day of April, 1930.

ROBERT C. BURT.

